The invention pertains to a method for detecting an illicit use of a security processor used for descrambling different multimedia contents disseminated on several respective channels. The invention also pertains to this security processor as well as to an information-recording medium to implement this method.
There are methods known to the filing party for detecting an illicit use. These methods include:                the reception by the electronic security processor of ECMs (Entitlement Control Messages) denoted as ECMi,t to descramble a temporal sequence of cryptoperiods of a scrambled channel i, each message ECMi,t containing at least one cryptogram of a control word CWi,t enabling a cryptoperiod CPi,t of the channel i to be descrambled, where i identifies the channel and the index t is a order number or sequential number,        each time that the security processor receives a new message ECMi,c, checking that the message ECMi,c is received within a predetermined time slot immediately consecutive to the preceding message ECMi,p received by this security processor for the channel i where the indices c and p are two specific values of the order number t,        
The term “time slot immediately consecutive to the preceding message ECMi,p” designates a time slot of predetermined duration starting immediately after reception of the message ECMi,p.
The term “multimedia content” designates an audio and/or visual content that is to be rendered in a form directly perceptible and comprehensible to a human being. Typically, a multimedia content corresponds to a succession of images forming a film, a television broadcast or advertisements. A multimedia content can also be an interactive content such as a game.